The head of the United States National Security Agency defended the dragnet phone surveillance program carried out by his office during a Senate hearing Wednesday afternoon on Capitol Hill.

Gen. Keith Alexander, the NSA director and head of the US Cyber
Commander, told the Senate Appropriations defense subcommittee
that the collection of personal data pertaining to millions of
Americans helped the NSA thwart a number of terror plots from
ever unfolding both domestically and abroad.

“Its dozens of terrorist events that these have helped
prevent,” Alexander told Sen. Patrick Leahy (D-Vermont)
during the hearing.

Wednesday’s hearing on the Hill was scheduled to focus heavily on
Alexander’s role with protecting the US cyber infrastructure, but
the NSA scandal exposed less than a week earlier took center
stage shortly after the general finished reading his opening
remarks and Sen. Leahy began grilling him over a leaked program
called PRISM and another surveillance operation that intercepts
the online communications of US citizens. Soon other lawmakers
joined in, using the opportunity to speak with the Obama
administration cyber czar about PRISM and other claims made by
29-year-old NSA leaker Edward Snowden, including that he could
“wiretap anyone, from you or your account to a federal judge
to even the president” from the NSA’s systems.

“False,” Alexander answered Congress of the allegation.
“I know of no way to do that.”

Alexander said he plans to give Congress more accurate numbers
about the alleged terrorist attacks foiled by the NSA, but
acknowledged his office has had issues with being open with the
public about the sensitive program in light of a recent scandal
that has taken twist after turn following the release of
classified documents by the UK’s The Guardian last week.

“I want the American people to know that we are trying to be
transparent here,” Alexander pleaded during the hearing.

The Guardian leaks, which began last Thursday, revealed that
millions of Americans had their personal phone call data sent to
the government through PRISM. Snowden has since gone into hiding
after taking credit for leaking the documents to Glenn Greenwald
of the Guardian, and a US Department of Justice investigation is
now underway.

Later in the hearing, Sen. Mark Udall (D-Oregon) asked Alexander
if he could ensure the NSA cooperates with any investigation into
possible civil liberties or privacy violations caused by the
surveillance programs, a request of which the general answered in
the affirmative — but not before rejecting allegations of abuse.

“I think you bring up a very important point here, because I
do think what we’re doing protects Americans’ civil liberties and
privacy,” Alexander said. “To date, we have not been able
to explain it because it’s classified. How do we explain this and
still keep this nation secure? That’s the issue that we have in
front of us.”

Indeed, even members of Congress wanted more answers from
Alexander during Wednesday’s hearing, and often lawmakers
interrupted the NSA chief to have him clarify what powers exactly
his agency is capable of. Sen. Jeff Merkley (D-Oregon) was one of
the politicians who pushed Alexander to answer why the NSA is
allowed to collect intelligence of all sorts at all times and
often with little explanation.

“We have several standards of law” to make those requests,
Sen. Merkley said, noting that investigators must show reasonable
grounds for a relevant, authorized investigation and a valid
statement of facts before submitting requests for intelligence.
The latest scandal, however, goes to show that tomes of data have
been detained by the government using overly broad excuses to
conduct blanketing surveillance.

“What authorized investigation gave you the grounds for
acquiring my cell phone data?” Merkley asked Alexander while
gesturing with his mobile device.

“On the legal standards and stuff, on this part here, I think
we need to get the Department of Justice and others, because it
is a complex area,” Alexander responded.

Sen. Dianne Feinstein (D-California), told Alexander that he must
respond in full to Merkley’s question in time for a separate
hearing scheduled on Thursday. At that point Alexander is
expected to answer more questions at length about PRISM and other
NSA surveillance programs during a closed-door discussion, but on
Wednesday he hinted that the disclosures so far have been more
than just damaging to the administration.

“There is no doubt in my mind that we will lose capabilities
because of this,” he said. “Our security is jeopardized.
We are less secure than two weeks ago.”

The White House confirmed that a Justice Department investigation
is underway, and Snowden is expected to be charged with espionage
for leaking classified intelligence.